In the integrated circuit (IC) industry, buried reflective mirrors are being researched for embedded use under integrated circuit (IC) semiconductive photodevices. In a first prior art embodiment, a dielectric reflector is formed on top of a semiconductor substrate and lithographically patterned and etched. After the mirror is lithographically patterned to create exposed sidewalls of the mirror, exposed portions of the substrate adjacent the sidewalls are epitaxially grown vertically upwards along the sidewall of the reflective mirror. After a significant period of time the vertical epitaxial growth will extend the substrate material up to a top surface of the previously patterned mirror. If growth continues from this point, lateral epitaxial growth begins to occur over a top surface of the patterned mirror. Eventually, after a very long epitaxial growth time, the entire top surface of the patterned reflective layers are completely covered with epitaxial silicon. In summary for this process, vertical epitaxial growth is followed by horizontal epitaxial growth in order to entirely encapsulate the mirror in semiconductive material.
It is important to note that these devices that utilize extensive vertical epitaxial growth as well as extensive lateral epitaxial growth are nonoptimal. First, vertical and horizontal epitaxial growth will increase the distance the epitaxial material must travel and forces epitaxial materials to turn corners during growth at right angles whereby silicon defectivity and epitaxial faceting is highly likely. In addition, the extensive time period needed for such epitaxial growth will reduce throughput through a fabrication facility whereby the cost of these devices will increase. Therefore, for high performance, high yield, low cost, and optimal devices, these types of vertically and horizontally epitaxially encapsulated reflective devices are not optimal.
In conjunction with the above method, the industry has begun to experiment with reflectors made entirely of metal where such metallic materials are located below the epitaxially grown semiconductive regions. While metallic reflective regions may be utilized as reflector devices, metallic reflectors are generally less efficient than a dielectric mirror or a combination of a dielectric and metallic reflector. In addition, there is no known method for forming composite metallic and dielectric reflectors without epitaxial growth or with reduced epitaxial processing whereby epitaxial defectivity and silicon faceting can be avoided.
Therefore, a need exists in the industry for an improved method of forming buried dielectric and composite dielectric/metallic reflective mirrors whereby silicon defectivity and faceting problems, as well as long time period and high temperature epitaxial processes, are reduced or avoided. In addition, it would be beneficial if the new process improved throughput and/or reduced wafer costs. In addition, these improved processes should allow for greater quantum efficiency, improved speed, and/or improved yield of the manufactured photoelectric devices.